An engine no start condition may occur or low fuel pressure DTCs may set after replacing the fuel injection pump on some 2019-2026 Silverado 1500, Sierra 1500; and 2021-2026 Tahoe, Suburban and Yukon models equipped with the 3.0L diesel engine (RPO LM2, LZ0). These conditions may be caused by the fuel injection pump not being properly timed to the crankshaft and camshafts of the engine.
The fuel injection pump input shaft on the 3.0L diesel engine has a keyway that aligns with a key in the timing gear. (Fig. 12) It is critical that the key aligns with the keyway for proper operation of the engine.
Fig. 12
Fuel Injection Pump Operation
The 3.0L diesel engine uses a two-cylinder fuel injection pump. Each cylinder has a fuel regulator that sends fuel into a shared fuel rail. Because of the timing chain gearing between the crankshaft and the fuel injection pump, one pump piston reaches top dead center during each of the engine cylinder’s power strokes.
For the engine to run correctly, the fuel pulse from the injection pump must line up the moment the fuel injector opens for the cylinder that is firing. If this timing is off even slightly, the DTCs may set or the engine may not start.
Checking Timing
When working on an engine that has low-pressure codes or won’t start after replacing the fuel injection pump, check the timing with a PicoScope. To do this, connect the scope to the fuel rail pressure sensor. Look at the pressure pulse from the injection pump and the fuel injector pulse. On a properly timed engine, the injection pump pulse (Fig. 13, A) will be aligned with the fuel injector pulse. (Fig. 13, B)
Fig. 13
On an improperly timed engine, the injection pump pulse will not be aligned with the fuel injector pulse. (Fig. 14)
Fig. 14
Installation Tips
When replacing the injection pump, ensure the keyway on the pump input shaft on the engine aligns with the key in the timing gear.
To aid installation, mark the new fuel pump shaft in the same position as the marks on the old fuel pump to ensure it is timed correctly with the engine timing. Use the marks on the pump shaft and the sprocket to align and install the new fuel injection pump. (Fig. 15)
Fig. 15
For additional information, refer to Bulletin #26-NA-176.
– Thanks to Larry Yaw
